1H NMR studies on intramolecular hydrogen bonding in perchlorates of N‐(pyridyl)amides of 6‐methylpicolinic acid N‐oxide

Abstract The 1 H NMR spectra of perchlorates of N ‐(pyridyl)amides of 6‐methylpicolinic acid N ‐oxide (PYAP) in CD 3 CN at 100 MHz show two proton signals belonging to two distinct intramolecular hydrogen bonds. The position of these signals is independent of concentration and temperature. That of the proton of the NH ⃛O bond in PYAP is shifted to still lower field than in N ‐(pyridyl)amides of 6‐methylpicolinic acid N ‐oxide (PYA) due to the inductive effect of the pyridine cation and the formation of another intramolecular hydrogen N + H ⃛O bond. The proton of the N + H ⃛O bond interacts strongly with its environment and is highly sensitive to traces of water. Presumably, water leads to dissociation of the intramolecular bond.